Evaluation of suspected pituitary pars intermedia dysfunction in horses with laminitis.

This research article investigates the prevalence and symptoms of pituitary pars intermedia dysfunction (PPID) in horses suffering from laminitis, a painful hoof condition. The study found that PPID was quite common among these horses and that they may have PPID even without demonstrating other typical symptoms.

Methods

• In this case series, 40 horses suffering from laminitis were selected. These horses had survived an initial episode of pain and were not on any medications that could affect the hypothalamic-pituitary-adrenal axis.
• These horses were then tested for PPID by evaluating the endogenous plasma ACTH concentration, i.e., the level of a hormone called adrenocorticotropic hormone in their blood.
• Various factors were recorded, including the horse’s age, suspected cause and duration of laminitis, degree of lameness, pellet bone rotation, and physical examination findings. Additional endocrine function tests were also conducted, and the treatment procedure, the ultimate outcome, and postmortem examination findings were noted.

Results

• The study found that 70% of the horses, or 28 out of 40, showed a high plasma ACTH concentration suggesting PPID.
• The median age of horses suspected of having PPID was slightly higher at 15.5 years, as compared to 14.5 years for those without PPID.
• Interestingly, laminitis occurred most frequently in horses with suspected PPID in September and for horses without PPID in May.
• It was also found that chronic laminitis was significantly more common in horses suspected of having PPID. This could possibly indicate a link between PPID and recurrent episodes of laminitis.
• Common physical symptoms in horses suspected of having PPID included abnormal body fat distribution, bulging supraorbital fossae (space above the eyes), and excessive hair growth (hirsutism). However, five horses displaying high ACTH levels showed no clinical abnormalities besides laminitis, suggesting that horses can have PPID even in the absence of other common symptoms.
• Treatment outcomes indicated that more horses with PPID that were treated with the drug pergolide survived, as compared to those that were not treated.

Conclusions

• Based on these findings, it can be concluded that PPID is quite common in horses with laminitis, especially in a primary-care ambulatory setting.
• Importantly, the research highlights that horses suffering from laminitis may have PPID even if they do not display other commonly associated symptoms. This underscores the importance of proactive testing for PPID in horses with laminitis.